High-temperature semiconductor processing chambers are used for depositing various material layers onto a substrate surface or surfaces. Typically, one or more substrates or workpieces, such as a silicon wafer, are placed on a workpiece support within the processing chamber to be processed. Both the substrate and workpiece support are heated to a desired temperature. In a typical processing step, reactant gases are passed over each heated substrate, whereby a chemical vapor deposition (CVD) or an atomic layer deposition (ALD) reaction deposits a thin layer of the reactant material in the reactant gases on the substrate surface(s). Through subsequent processes, these layers are made into integrated circuits, and tens to thousands or even millions of integrated devices, depending on the size of the substrate and the complexity of the circuits.
Various process parameters must be carefully controlled to ensure the high quality of the resulting deposited layers. One such critical parameter is the temperature of the substrate during each processing step. During CVD, for example, the deposition gases react at particular temperatures to deposit the thin layer on the substrate. If the temperature varies greatly across the surface of the substrate, the deposited layer could be uneven which may result in unusable areas on the surface of the finished substrate. Accordingly, it is important that the substrate temperature be stable and uniform at the desired temperature before the reactant gases are introduced into the processing chamber.
Similarly, non-uniformity or instability of temperatures across a substrate during other thermal treatments can affect the uniformity of resulting structures on the surface of the substrate. Other processes for which temperature control can be critical include, but are not limited to, oxidation, nitridation, dopant diffusion, sputter depositions, photolithography, dry etching, plasma processes, and high temperature anneals.
Methods and systems are known for measuring the temperature at various locations near and immediately adjacent to the substrate being processed. Typically, thermocouples are disposed at various locations near the substrate being processed, and these thermocouples are operatively connected to a controller to assist in providing a more uniform temperature across the entire surface of the substrate. For example, U.S. Pat. No. 6,121,061 issued to Van Bilsen teaches a plurality of temperature sensors measuring the temperature at various points surrounding the substrate, including a thermocouple placed near the leading edge of the substrate, another near the trailing edge, one at a side, and another below the substrate near the center of the substrate.
Thermocouples are a type of temperature measuring device often used in semiconductor processing reaction chambers to measure temperatures at various locations around the substrate being processed and within the reaction chamber in general. Thermocouples typically include at least one junction formed by fusing the ends of multiple wires together, wherein the wires are formed of at least two dissimilar metals to that a thermocouple is formed therebetween. The thermocouples are installed within the reaction chamber to ensure that the junction(s) of the thermocouple are precisely located to provide a temperature measurement at a particular location. When the junction of the thermocouple is offset from the precise location during installation, the temperature data provided by the thermocouple is less accurate the farther away the junction is from the desired location. Additionally, for thermocouples having multiple junctions located along the length thereof, rotation of the thermocouple may also cause the junction to be located further away from the desired location.
Typically, when thermocouples commonly known in the art are manufactured, there are no features that positively locate the junction within the thermocouple. Also, when thermocouples are installed within the reaction chamber of a semiconductor processing apparatus, there are no features on thermocouples commonly known in the art to ensure that the thermocouple is properly aligned within the apparatus to such that the junction(s) is located at a precise location for a temperature measurement.
Accordingly, there exists a need for a thermocouple having internal alignment features that allow the junction to be consistently located within the thermocouple during manufacture. There also exists a need for a thermocouple having external alignment features that allow thermocouples to be positively located within a reaction chamber during installation.